Distillate fuel composition



United States Patent F DISTILLATE FUEL COMPOSITION Martin Hamer, Chicago, 111., assignor to Standard Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Filed Apr. 26, 1955, Ser. No. 504,087

2 Claims. (CI. 44-69) My invention relates to improvements in the suppression of surface ignition of leaded gasolines in the operation of internal combustion engines. More particularly, my invention provides a novel additive combination, which incorporated in gasoline, is effective in suppression of surface ignition.

Current emphasis on high compression ratios, and other high performance design features, in gasoline engines of the internal combustion type has tended to raise not only octane requirements but has created a situation where knock from surface ignition, often referred to as preignition, has become a limiting factor in engine design and operation. Knock induced by surface ignition appears to be a concomitant of the use of tetraethyl lead as the anti-knock agent in fuels of high performance value. When motor fuels containing tetraethyl lead are burned in internal combustion engines, deposits consisting of carbonaceous material and lead salts are continuously formed in the combustion chambers. These deposits are harmful in that they increase the octane requirement of the engine by inducing knock and causing preignition. Apparently preignition, that is the ignition of the fuel charge before passage of the spark, is caused by glowing of the carbon in the deposits. Moreover, lead salts are known to cause carbon to glow at a significantly lower temperature than the glow point of carbon alone.

I have discovered that the presence of aluminum and phosphorus in the combustion chamber suppresses the glowing of carbon; i.e., increases the glow point, and hence acts to suppress knock induced by surface ignition. According to my invention, an additive combination essentially comprising an oil soluble aluminum compound and an oil soluble phosphorus compound is provided. Advantageously, the additive combination is made up in the form of a concentrate in a solvent oil vehicle. The concentrate then may be conveniently added in small quantities to finished gasolines containing tetraethyl lead,

thus providing. finished gasoline blends inhibited against.

knock induced by surface ignition.

I have found, in the course of my investigations, that it is essential to provide the combination of aluminum and phosphorus in the combustion chamber if suppression of knock by surface ignition is to be significantly controlled. 1 have also'found that the nature of the aluminum compound does not appear to be controlling, provided that it is sufliciently oil soluble for use in gasoline, since control tests have shown that aluminum oxide appears to be the effective factor in raising carbon glow point. It is believed that, in the engine, any oil soluble, organic aluminum compound is converted to aluminum oxide. Similarly, I have found that the criterion of utility for the phosphorus component is oil solubility to an extent permitting its use in gasoline rather than the particular nature of any particular phosphorus compound.

In producing the additive combination of the invention, the relative properties of the aluminum containing and phosphorus containing components are desirably se- 2,938,776 Patented May 31, 1960' lected to provide approximately equimolar proportions of aluminum oxide (A1 0 and phosphorus pentoxido (P 0 upon combustion. These proportions, however, can be varied considerably, say from about 90 parts of one to 10 parts of the other, while retaining the benefits of the invention. The additive combination may be made up in any suitable solvent oil facilitating blending into finished gasoline, for example, naphtha, light gas oil, catalytic cycle oil, light lubricating oil fractions, or aromatic solvents such as benzene, toluene, xylenes and the like. The additive may be blended into leaded gasoline, usually containing from about 1 to 3 ccs.-of tetraethyl lead per gallon in concentrations from about 0.0001 to 0.1 weight percent of the additive on an oil free basis.

The invention is applied with the greatest advantage to premium motor gasolines, which usually boil in the 100 to 350 F. range, but it may be employed with broader cut gasolines and even fuels of somewhat higher boiling.

A particularly convenient form for the phosphorus component is tricresyl phosphate since it has desirable oil solubility and is available on a commercial scale. Other oil soluble phosphorus compounds such as tris-chloropropyl thionophosphate, the dialkyl dithiophosphites and various trialkyl and triaryl phosphates, phosphites and phosphonates have value. It should be noted that because finished gasoline blends ordinarily contain other additives such as anti-oxidants, gum inhibitors, anti-rusts and dyes, the compatibility of the aluminum and phosphorus compounds used according to the invention with these additives should be considered. Also, phosphorus compounds containing sulfur may be somewhat less desirable than those that are sulfur free because of the deleterious effect of sulfur on the lead response of the gasoline stock, that is to improvement in Octane number by addition of tetraethyl lead. V

The effectiveness of aluminum and lead in reducing the glow of combustion chamber deposits was evaluated on a bench scale by determining the glow point, or 10 second ignition delay temperature, of the sample under examination. The test was carried out by placing the sample of either carbon or combustion chamber deposit +additive on a stainless steel dish which had been heated in an open pot type furnace to a specified temperature.

The temperature was indicated by means of a thermocouple which was placed inside a well extending from the outside to the center of the sample dish. The time required for visible glow (ignition) of the sample to occur was measured by means of a stopwatch. That temperature at which the sample glowed 10 seconds after being placed on the steel dish was recorded as the glow point.

In extensive glow point testing it was determined that although lead phosphate, presumably the end product of an organic phosphorus compound in the combustion chamber, reduces the glow point of pure carbon, it is ineffective in reducing the glow of either carbon plus lead chloride, presumably present from decomposition of tetraethyl lead, or of actual combustion chamber deposits. On the other hand, it was found that the combination of aluminum oxide, presumably the end product only pure carbon but also carbon plus leadchloride and actualcombustion chamber deposits; The illustrative data-are-tabulatedbelow:

' 10 sec. ignition delay temp. F.)

Carbonalone 1130.

Carbon- +Pb (PO No glow at 1130. Carbon +Al O No glow at 1130. Carbon- +A12O3.P2O5 NO glOW at Carbon +PbCl 800; Carbon-+PbCl +Pb (PO 800. Carbon Carboh-l-PbCl +Al O .P O 1000.

Combustion chamber deposit alone 730. Combustion chamber deposit ;+Pu P0,) 750. Combustion chamber deposit ;+A1,o, 750. Combustion chamber deposit Q+AI O .P O 840.

an additive combination, illustrative of the invention, was evaluated in a Pontiac engine using a cycled-load procedure under the following operating conditions:

once an hour a Duration 45 sec. 135 sec Q93 2%? Cycle Engine Speed. 700 r.p.m. 2,000 r.p.m throttle accelr oad none 26 lbs eration for 30 see.

Compression ratio 7.6:1. AirFuel ratio- As found. Test duration 150 hours. Coolant temp 1605 F. Oil Tempo l65=l=10 F.

Example I In this example, leaded gasoline containing 3.0 cc. per gallon of TEL was inhibited by the addition of tricresyl phosphate, using 0.1 mol of that theoretically required for reaction with the tetraethyl lead when the mixture' isburned' in the combustion chamber, and 0.0375 percent byweight of aluminum naphthenate. In tests with a 1953 Pontiac S-cylinder engine using a 165 hour cycled load procedure under the above conditions, the additive combination of the invention was found to efiect a substantial reduction in preignition, together with a decrease in the normal octane requirement increase. The

Example 11 In this example, the eifect of the phosphorus and aluminum compounds used separately was compared to the use of the additive combination. The fuel was a leaded gasoline containing 3.0 cc. per gallon of tetracthyl lead. In the following tabl e, re sults with the base fuel are tabulated in column 1 results-with the base fuel con- '-taining tricresyl phosphate in an amount equiyalent to e4 of that theoretically required to form lead phosphate in -the'combustion chamber 'are tabulated in column' 2;

results with the additive combinatiomusing 0.1 theoretical unit of tricresyl phosphate and 1 an equimolar proportion of aluminum naphthenate, are tabulated in column 3; and results with the base fuel containing aluminum naphthenate alone in an amount equivalent to the amount of tricresyl phosphate as in column 2 are tabulated in column 4. The tests were conducted with a 1953 Pontiac engine in a manner similar to thatof Example I. It will be noted fromthetabulated data 'that the use of the additive combination produceda significant reduction in preignitioncount and octane requirement increase whereas the use ofeitherofthe components separately peared tobe relatively ineifective.

Preignition Count .Q 147 102 50 115 OBI 5.0 3.5 2.0 5.0 Total Deposit (g.) 94.4 97.3 93.2 90.0

I claim: r 1. A distillate fuel comprising a major proportion of gasoline containing tetraethyl lead and a minor proportion of an additive combination essentially comprisingessentially comprises from. about 10 to parts of aluminum naphthenate, from about 10 to 90 parts of tria cresyl phosphate, and a sufiicientamount of a solvent oil to provide fluidity.

References Cited in the file of this patent UNITED STATES PATENTS 2,086,775 

1. A DISTILLATE FUEL COMPRISING A MAJOR PROPORTION GASOLINE CONTAINING TETRAETHYL LEAD AND A MINOR PROPORTION OF AN ADDITIVE COMBINATION ESSENTIALLY COMPRISING FROM ABOUT 10 TO 90 PARTS OF ALUMINUM NAPHTHENATE AND FROM ABOUT 10 TO PARTS OF TRICESYL PHOSPHATE, SAID ADDITIVE COMBINATION BEING IN AN AMOUNT SUFFICIENT TO REDUCE SUSCEPTIBILITY OF THE LEADED GASOLINE TO SURFACE IGNITION. 